(1) Field of the Invention
The invention relates to a pressure balanced, slow actuating device for manipulation of an auxiliary tool, such as a mechanically set packer, tubing or casing hangar, or an inflatable packer or bridge plug, or the like.
(2) Brief Description of the Prior Art
It has become apparent in recent years that in order to improve the success rate in the sealing of packers, bridge plugs and the like, it is advantageous to have a slow setting cycle, resulting in a comparatively slow, continuous stroke upon the actuating mechanism from the beginning of the setting cycle until its completion. Many subterranean well packers and bridge plugs contain anti-extrusion elements which are inelastic, i.e., the performance or characteristics depend upon the rate at which deformation occurs, as well as the rate of load application. Such components effective operation is very time dependent and it is desirable to deform them slowly to control physical properties during deformation. In the past, a lengthened time cycle for the activation of subterranean well auxiliary tools, such as packers, bridge plugs, tubing and casing hangers, safety valves, fishing tools, and the like, as well as manipulation of pressure setting mechanisms utilized to initiate the manipulation of such auxiliary tools (all hereinafter referred to as "auxiliary tool") has been achieved by the utilization of a slow burning power charge to build up pressure comparatively slowly within a chamber, resulting in the time of the setting or actuating cycle being approximately equivalent to the burn time of the power charge. The power charge would be ignited by conventional means, such as electric line igniting elements, well known to those skilled in the art, to fire the power charge resulting in the fracturing of slips, if used in conjunction with a mechanically set packer, bridge plug or the like, to initiate the stroking mechanism and resulting sequential steps. The power charge results in an increase in internal pressure within a chamber to sever or shear a tension bolt to initiate the sequential setting mechanisms. The auxiliary tool, such as a packer, will entrap energy resulting from the compression of the elastomer which, in turn, applies a hydrostatic pushing stress against the internal diameter of the conduit or wall upon which the tool is to be set, resulting in a hydraulic seal.
The characteristics and resisting forces of packing elements and the accompanying anti-extrusion elements are significantly different when deformation occurs over a comparatively extended period of time when compared to those characteristics when the setting procedure occurs over only a few seconds time interval due to the inelastic nature of the utilized elastomer. A rapid deformation will result in fluid being trapped between the elastomer and the casing or between the elastomeric packing element and the anti-extrusion element. After setting, the trapped fluid may escape, resulting in a loss of energy required for proper setting. The elastomeric elements have a tendency to fill the area where the previously trapped fluid was contained. Accordingly, when such elastomeric materials flow into these void spaces, the state of compressive stresses resulting from the application of hydrostatic pressure within these fluids is relaxed, resulting in a serious loss of setting integrity through the auxiliary tool, such as the packer. In more serious instances, the tool, such as the packer, not only will become unsealed, but will become unset and may fall downwardly in the well, resulting in a costly and time-consuming fishing trip or, even worse, the total loss of the well.
The use in the past of slow burning power charges which increase the setting cycle from a few seconds to one or more minutes has been utilized to abate these very serious problems. Such power charges are commercially available and well known to the industry. Typical of such devices is the Model "E-4" Wireline Pressure Setting Assembly, Product No. 437-02 of Baker International Corporation. The power charge in this setting tool is actuated by means of an electric line which ignites the power charge, causing stroking of a piston which is extended to a setting mandrel, or the like, to the auxiliary tool. The pressure setting assembly is secured at its lower end to the upper most end of the auxiliary tool to be set or actuated within the subterranean well.
While the use of slow burning power charges is intended to assure the satisfactory setting of tools, as described above, such mechanisms solve one problem, but create others. For example, the temperature at setting depth of a typical auxiliary tool in most subterranean wells throughout the world is approximately 150.degree. F. and in such cases the burn/setting cycle is typically within a satisfactory time frame of from between about 30 to about 45 seconds. However, in stark contrast, as the temperature of the well increases, the burn/setting cycle time is decreased substantially, such that it may be reduced to about 20 seconds in temperature environments of about 300.degree. F. and may be reduced to from between about 200 milliseconds to about 2 seconds when temperatures of about 400.degree. F. are encountered, thus almost totally defeating the purpose of the utilization of such power charges for long cycling setting operations. Moreover, at such higher temperatures, some power charges may even explode, as opposed to burn, giving off contaminating gas as the result ol the relatively low order of ignition. An explosion, as opposed to a deflagration, thus occurs.
An additional problem encountered frequently in the use of power charge mechanisms for the setting of auxiliary tools in subterranean wells is the requirement for radio silence prior to, during and subsequent to the setting operation in order to avoid and inadvertent or premature activation of the power charge. Oftentimes, many hours are required to run the setting assembly on electric line with the auxiliary tool to the proper setting depth in the subterranean well, and an equal amount of time is required to retrieve the electric line. Safety requirements mandate complete elimination of all radio communications during such operations. Finally, disassembly of such setting assemblies incorporating power charges subsequent to the setting operation can be extremely dangerous to operating personnel as a result of trapped pressure within the device.
The present invention remedies many of the problems associated with conventional and prior art power charge pressure setting devices by providing a device which does not require the use of explosives. The device of the present invention can provide extended period setting cycle times regardless of the temperature environment at the setting or manipulation depth for the auxiliary tool in the subterranean well. Furthermore, there is no trapped pressure within the device when it is returned to the surface of the well.
The device of the present invention will provide an exceptionally long stroke capability, as well as volume capability, which may be adjusted to accommodate the particular size and operation of the auxiliary and other tools. The device does not yield toxic waste products which are commonly associated with conventional power charges. The device is capable of running and setting conventional packers as well as inflatable packers with a battery operated slickline power or other supply. It may be deployed on electric or wire line and is selectively initiated. Since it is not dependent upon power charges, radio silence is not required during running in, actuation, or retrieval of the device in the well.